1. Field of the Invention
The present invention relates to a process and apparatus for producing pig iron in a blast furnace with reduced feed of specific coke and employing exchange fuel gas obtained by partial oxidation of fine grained to dusty fuel with oxygen and/or air and possibly steam.
2. Description of the Prior Art
It is conventional to save coke in the blast furnace process within certain limits and to substitute exchange fuels such as natural gas or heating oil. The exchange fuels are usually together with the hot blast, fed through blow molds into the blast furnace and are there initially substantially oxidized. This generates the heat required for the endothermal reactions proceeding in the coke zone of the blast furnace: EQU C+CO.sub.2 .fwdarw.2CO (1) EQU C+H.sub.2 O.fwdarw.CO+H.sub.2 ( 2)
These reactions provide the reducing gases for the indirect reduction of the iron oxides in the blast-furnace stack according to the equation: EQU FeO+CO(H.sub.2).fwdarw.Fe+CO.sub.2 (H.sub.2 O) (3)
The direct employment of reduction gases, which are substantially gas mixtures containing carbon monoxide and hydrogen, therefore reduces the use of carbon supplied as coke according to equations (1) and (2). At the same time the heat needed for these endothermal reactions is unnecessary as a result of the addition of the reducing gases. If it is possible to feed the reducing gas as a hot gas to the blast furnace, this allows to save an additional important part of the warm up heat of the blast furnace. This effects at the same time a considerable reduction in the need for hot blast and therefore of the total gas volume and enables a considerable increase in the efficiency of the blast furnace in addition to the savings in coke. This is the case in particular where the reducing gas carries few load components such as for example nitrogen in the blast furnace.
For producing the reducing gases the gasification of fine grained to dusty fuels with oxygen and/or air and possibly with steam can be applied according to the flight stream principle. The produced raw gas upon leaving of the gasifier has a temperature of about 1200.degree. C. and contains in addition liquid to viscous slag particles and hydrogen sulfide as an impurity.